The polyphenylene ethers and processes for their preparation are known in the art and described in numerous publications, including Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875. Other procedures are described in the Bennett and Cooper patents, U.S. Pat. Nos. 3,639,656, 3,642,699, 3,733,299 and 3,661,848. All of these patents are incorporated herein by reference.
The processes most generally used to produce the polyphenylene ethers are based on the self-condensation of a monovalent phenol in the presence of an oxygen-containing gas and a catalyst. Inorganic bromides have been described as promoters for this reaction in the above-noted U.S. Pat. Nos. 3,733,299, and onium compounds have been mentioned in U.S. Pat. Nos. 3,365,422 as promoters for this reaction in the absence of free water.
It has now been found that the use of a critical maximum amount of a quaternary ammonium salt will reduce the amount of time required to produce a polymer having a commercially useful molecular weight over the time required to produce the same molecular weight polymer, if this material is not employed in the catalyst system, provided that an aqueous phase is present in the reaction zone. This is accomplished by the use of less than the disclosed amount of onium compound that is used in U.S. Pat. No. 3,365,422 and without the water-free conditions that are taught by that reference.
U.S. Pat. Nos. 3,549,670 relates to the oxidation of phenols with a metallic copper-nitrogen base catalyst in a particular solvent system. High concentrations of the nitrogen base materials are used in the disclosed reaction and these materials do not act as reaction promoters.
It has been found that for a given quantity of copper-salt amine catalyst, the combination of an alkali metal bromide or alkaline earth metal bromide and a quaternary ammonium salt will produce a polymer of higher molecular weight that it is possible to produce with the use of a single promoter irrespective of the length of time the reaction is run.
It has also been found that the total amount of copper-salt amine catalyst may be reduced in connection with the oxidative coupling of di-ortho-substituted phenols when a combination of an alkali metal bromide or alkaline earth metal bromide and an ammonium salt are employed as promoters for said copper-salt amine catalyst system.
These and other advantages of this invention will be apparent from a reading of the detailed description of the invention.